|I know this post is a little old, but I thought that I'd add my 2 cents. |
First off all, I am surprised that you even have Avast set to scan Exchange folders. This goes against best practices as published by Microsoft as well as most Anti-virus manufacturers. Most of the Microsoft Exchange folders should be excluded from on-access and scheduled scanning. See here for a list of files, folders, and processes that Microsoft recommends should be excluded.
To adequately protect an Exchange server, whatever antivirus program is installed on the server should be designed for servers and feature an Exchange anti-malware component. This will properly hook into the Exchange system and scan all messages. This will prevent infected messages from being sent/received as well as protect the integrity of the mail stores.
In your case, the appropriate product from Avast is called Avast! Email Server Security. Details can be found here.
I would highly recommend AGAINST allowing your current Avast! scanner from trying to clean the .edb file. If you choose to do so, PLEASE make sure you have a complete backup of the entire exchange system (both brick level backup as well as database) and make a copy of the .EDB file once the information stores are offline with ALL exchange services stopped. Recovering from a corrupted .EDB file is a PAIN!
Let me know if you have any questions or need more info.
IT Desktop & Network Consultant - MOS Master Certified, MCP, MCSA, MCITP - Windows 7, CCNA Certificate Pending, A+, Network +